Supramolecular aggregates of sulfonated derivatives of tetraphenylporphyrin as tentative asymmetric counteranions in organocatalysis

Abstract

On this research project it has been studied the viability of using supramoleculary chiral aggregates of sulfonated self-assembling porphyrins as chiral counter anions on Michael and Diels-Alder organocatalytic reactions on water, which proceed through a cationic reaction intermediate to determinate the feasibility of using a ACDC (Assymetric counteranion directed catalysis) strategy to transfer the supramolecular chirality of the aggregates on an organic reaction product enantiomeric excess. To do so, a method to prepare the chiral aggregates of the meso-5,10,15,20-tetrakis(4-sulfonatofenil)porphyrin on its zwitterionic form has been optimized in order to prevent the presence of other counter anions which could also interact with the cationic intermediates from the organocatalytic reactions. It has been proved that the zwitterionic porphyrin not only maintains the aggregation state of the sodium salt, also, the supramolecular chirality still remains even though the addition of the basic organocatalistys (pyrrolidine and isoindoline). Finally it has been shown for the studied Michael and Diels-Alder reactions, exists a narrow window of experimental conditions where it is possible to use this catalysts under ACDC conditions.